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blackbonnie
03-20-2008, 01:59 AM
i have never built an enclosure with the port like this T where towards the back of the box instead of curving one way it splits to a T. how do you determine the port length that way? lets say that my port length for example needs to be 22" and my port can go back 10" and still stay away from the wall 4" which would be the width of the port. since i would still need 12" of port length would i cut that in half and run 6" to the right and 6" to the left? im pulling these numbers out of my head just as an example but would like to have a rough idea on how to calculate.

DBDRAGGUY
03-20-2008, 02:05 AM
i have never built an enclosure with the port like this T where towards the back of the box instead of curving one way it splits to a T. how do you determine the port length that way? lets say that my port length for example needs to be 22" and my port can go back 10" and still stay away from the wall 4" which would be the width of the port. since i would still need 12" of port length would i cut that in half and run 6" to the right and 6" to the left? im pulling these numbers out of my head just as an example but would like to have a rough idea on how to calculate.

You lost me
:confused:

blackbonnie
03-20-2008, 02:35 AM
where did i lose you at? take your time and read it, i felt like i explained myself well

blackbonnie
03-20-2008, 03:02 AM
up

blackbonnie
03-20-2008, 03:46 AM
would like to learn tonight

Blove1991
03-20-2008, 08:48 AM
I have wondered the same thing myself, it seems like your method would be correct. I either thought your way was right or that it had to go 12" both ways??? Your talking about a port in the middle of the box correct?

05F150SuperCrew
03-20-2008, 09:20 AM
not sure, but if u do the calculations for 2 ports at 4" and 1 at the original... subtract 10" from the total length u need for the 2 and that's what i'd think... don't listen to me thought, wait for someone who hasn't thought or heard of this for the first time this mornin...

Mr Cabinetry
03-20-2008, 01:20 PM
The kind of port design being referred to:

Where the main part of the slot port is wider and then splits off into a T at the back of the enclosure.

The parts of the T that split off are half the width of the main slot width. The length of the T section from the centerline of the main port are half the length of what the total length if the port.

So, for example, if the total length of the port was 40" and the main length of the centerline to the T was 20", that would leave 20" divided by 2 = 10". The T lengths would be 10" each by half the width of the main width of the port, completing the slot port.

http://i29.photobucket.com/albums/c251/MrCabinetry/Audioque&#37;2012%20%20Cntr%20Port/SD2512sCenterPort-1.jpg

Trixter
03-20-2008, 02:29 PM
The kind of port design being referred to:

Where the main part of the slot port is wider and then splits off into a T at the back of the enclosure.

The parts of the T that split off are half the width of the main slot width. The length of the T section from the centerline of the main port are half the length of what the total length if the port.

So, for example, if the total length of the port was 40" and the main length of the centerline to the T was 20", that would leave 20" divided by 2 = 10". The T lengths would be 10" each by half the width of the main width of the port, completing the slot port.

http://i29.photobucket.com/albums/c251/MrCabinetry/Audioque&#37;2012%20%20Cntr%20Port/SD2512sCenterPort-1.jpg

exactly....

BrianChia
03-20-2008, 03:32 PM
^^ The proper way to calculate it would be to figure the required port length for an enclosure of 1/2 the net volume and 1/2 the port port dimensions then merge the two ports at the center. If you treat it like one large enclosure your calculations will be off.

Actually, either way will not be completely accurate due to the complexities of the merging ports, but the first method I described will be much more accurate since the enclosure is no longer one shared chamber but two distinct chambers and the box volume/port length/port area relationships are not perfectly linear.

Immacomputer
03-20-2008, 03:45 PM
^^ The proper way to calculate it would be to figure the required port length for an enclosure of 1/2 the net volume and 1/2 the port port dimensions then merge the two ports at the center. If you treat it like one large enclosure your calculations will be off.

Actually, either way will not be completely accurate due to the complexities of the merging ports, but the first method I described will be much more accurate since the enclosure is no longer one shared chamber but two distinct chambers and the box volume/port length/port area relationships are not perfectly linear.

I agree. The best way to do it is to add a center support and just build two enclosures identically but mirrored.

tommyk90
03-20-2008, 03:47 PM
I agree. The best way to do it is to add a center support and just build two enclosures identically but mirrored.

Thats actually how I built one enclosure. It was a real pain in the *** and got stolen from the guys car 2 days later. :crap:

Would have been better off just doing the port off to one side. Don't have to deal with figuring out separate chambers and whatnot.

Immacomputer
03-20-2008, 04:29 PM
Ouch. When my car got stolen, I was more upset that they stole one of my enclosures than that they stole my IDQ 12!

Mr Cabinetry
03-20-2008, 04:53 PM
^^ The proper way to calculate it would be to figure the required port length for an enclosure of 1/2 the net volume and 1/2 the port port dimensions then merge the two ports at the center. If you treat it like one large enclosure your calculations will be off.

Actually, either way will not be completely accurate due to the complexities of the merging ports, but the first method I described will be much more accurate since the enclosure is no longer one shared chamber but two distinct chambers and the box volume/port length/port area relationships are not perfectly linear.

I'm not a big fan of this type of enclosure design just for the varying degree's of inaccuracy as you stated, plus the performance value of port design in general I find highly dubious that it would perform as well as tommyk90 & Immacomputer stated, better to do one large port to the side or just do two separate ported chambers and be done with it.

blackbonnie
03-20-2008, 05:59 PM
yeah well im gonna try to build one eventually and i will use cabinetry's method, i understood how he was explaining it and i think with a little work i could get it done. ive just never knew how you determined where and how far it split off. thank you though for explaining